Micro and Macro Level Thermal Decomposition Studies of Newspaper Waste

Transcription

1 International Journal of Emerging Technology and Advanced Engineering Micro and Macro Level Thermal Decomposition Studies of Newspaper Waste Namjoshi S.A 1, Rao V.J 2, Parikh J.K 3 Channiwala S.A 4 1 (Department of Mechanical Engineering Sardar Vallabhbhai National Institute of Technology, Surat) 2(Department of Metallurgy Engineering Faculty of Tech. & Engg. The M. S University of Baroda) 3 (Department of Mechanical Engineering Sardar Vallabhbhai National Institute of Technology, Surat) 4 (Department of Chemical Engineering Sardar Vallabhbhai National Institute of Technology, Surat) Abstract- Extraction of energy from Municipal Solid Waste (MSW) is difficult task because of its heterogeneous nature. It consists of components like papers, plastics, organic matter and non-combustibles; all having different decomposition rate depending upon their individual characteristics. Hence it is necessary to determine the degradation behavior of individual components to evaluate the kinetics of the reaction. The present work focuses on the decomposition of one of the major component of MSW i.e. newspaper waste (about 6-7% by wt) based on which the kinetic parameters are obtained at heating rates () 5, 7,1,15,2 C/min using TG/DTG 32 horizontal differential system balance mechanism. The three independent parallel reactions describing the decomposition have been considered to obtain the kinetic parameters. Residue left after decomposition is analyzed using elemental analysis and morphology techniques. The present data of TGA has been compared with decomposition of sample with Batch type pyrolyser (BTP) with sample of approximately 6 gm at heating rate 1 C/min in nitrogen atmosphere. The data thus gathered will be useful in the modeling, design and operation of thermal conversion processes for MSW. Keyword-Kinetic Study, Municipal Solid Waste, Newspaper waste, Thermo gravimetric Analysis I. INTRODUCTION The handling of Municipal Solid Waste (MSW) is a challenging task not only from economical but also from social point of view for the country like India where the waste generation is 96 million MT per year. [1, 2, 3] The composition of MSW varies due to life style of the society, economical growth, population and waste collection efficiency. The substantial increase in the solid waste generation resulting not only in the contaminating of air, water and land but its disposal is severe issue due socio economical problems [4]. The major compositions of MSW are compostable matter, polymers and non-combustion able items and out of which compostable matter and polymers waste which are 6% of total composition [1,2] having high energy content and particularly for India the Higher Heating Value (HHV) of MSW composition varies from 2.2 MJ to 17.2 MJ [2,3]. The only solution for such high energy content waste is to convert into energy using appropriate thermal degradation technique due to decreasing space availability for land filling and environmental constrains [4,5] The organic composition consists of papers from 7-9 % of total composition [1,3] which is lignocellulosic compositions and newspaper is one of the major composition. The conversion of newspaper into useful products and extraction of energy through pyrolysis of news paper is promising option and for to design such pyrolyser, the kinetic study is important. The kinetic study correlates the decomposition rate with temperature variation and the decomposition constants activation energy and preexponent factor are estimated using Arrhenius equation. A.N. Garcia et al [6] obtained the kinetic parameters for MSW pyrolysis. Wu et al [7] studied kinetics and pyrolysis of mixture of four papers (uncoated and coated printing paper, newsprint and tissue paper) for heating rates 1, 2, 5 K/min and results indicated that decomposition occurred in two stages. Sørum et al [8] reported decomposition of four types of papers and five different plastics at 1 C/min heating rate. The results indicate that the decomposition of papers occurred in three stages and plastic decomposition occurs in one stage except poly vinyl chloride with considering single reaction model with parallel, independent reactions. JIN Yu-qi et al [9] studied a new kinetic model with consideration that the number of weight loss stages equals to number of reactions. 313

2 International Journal of Emerging Technology and Advanced Engineering Wu et al [1] studied pyrolysis of newspaper with TGA system at a constant heating rate of 5 K min 1 and in a nitrogen environment and analysed pyrolysis products and the residues were collected by GC and elemental analyzer respectively. Bhuiyan et al [11] reported TGA studies for newspaper with heating rates 5, 1, 2 K/min for kinetic study and pyrolysis of newspaper waste. P.Grammelis et al [12] studied refuse derived fuel behavior by thermogravimetry under pyrolysis and combustion conditions. C. David et al [13] discussed pyrolysis phenomenon on the basis of a series of TGA experiments for cardboard. Kuen-Song Lin [14] aimed to obtain pyrolysis and kinetics of RDF to understand the role of its components on its pyrolysis behavior. Preliminary pyrolysis kinetics of RDF was investigated using a thermo gravimetric analyzer. Ch. Pasel [15] focused on pyrolysis of shredder waste as a possible way for chemical recycling of plastic wastes and deals with the technical requirements for an industrial application. S. Ojolo [16] suggested the pyrolysis as promising option for converting MSW into fuel and to manage wastes through volume reduction. Since waste-to-energy is good option and for designing incinerator, gasifier and pyrolyser for bio mass waste some information about pyrolysis and kinetics are required however for news paper waste data is not sufficient also kinetic study has been carried out at micro level but kinetic study at macro level has not been reported as per our knowledge. The aim of present work is to investigate the decomposition of newspaper of five heating rates () 5, 7,1,15,2 C/min in nitrogen atmosphere with Thermogravimetric analysis (TGA) for providing simple kinetic model with wide temperature of Room temperature (RT) to 6 C and also with heating rate of 1 C/min the kinetic study of newspaper with Batch Type Pyrolyser (BTP).Additionally the comparative decomposition study between TGA and BTP for heating rate of 1 C/min and elemental analysis of residue of newspaper for heating rate 1 C/min with scanning electron microscope (JEOL 561LV) using Energy Dispersive Spectroscopy (EDS). II. EXPERIMENTAL 2.1 Material The experiments were carried out on commercial newspaper and cuts into small pieces of 2-3 mm with the help of stainless steel scissors. The particle size is used in BTP is larger compare to TGA due no weight and size constrains of crucible. Table 1 shows proximate and ultimate analysis result and HHV of newspaper. Fixed Carbon TABLE I PROXIMATE ANALYSIS, ULTIMATE ANALYSIS AND HIGHER HEATING VALUE OF NEWSPAPER Volatile Matter Ash Carbon Hydrogen Nitrogen Sulfur Oxygen HHV MJ/Kg Thermogravimetric Analysis (TGA) The thermogravimetric and differential thermogravimetric analysis were carried out in SEIKO TG/DTA-32 thermal system. Samples have been scanned between room temperature to 6 C with heating rate of () 5, 7,1,15,2 C/min in nitrogen gas atmosphere and with 5 ml/min flow rate. The amount of sample is used maximum up to 6 mg. Samples are placed in platinum crucible and α alumina was used as reference. 2.3 Batch Type Pyrolyser Pyrolysis of newspaper is carried out in Batch Type. Pyrolyser (BTP) having PLC control system to obtain heating rate at different in temperature range of RT to 12 C. The concentric tube heat exchanger is used to condense the volatiles evolved in the reactor. The nitrogen purging rate is 2 l/min and heating rate is 1 C/min from RT to 6 C with sample size is approximately 6 gm. Two thermocouples are inserted to measure the temperature of heater as well as temperature of sample. 314

3 International Journal of Emerging Technology and Advanced Engineering Figure 1 Batch Type Pyrolyser III. KINETIC MODELING Non-isothermal kinetic study of weight loss under pyrolysis of carbonaceous materials is an extremely complex task because of the presence of numerous complex components and their parallel and consecutive reactions. The extent of conversion or the fraction of pyrolysed material, x, is defined by the expression m m x (1) m m f where m is the mass of the sample at a given time t; m and m f refer to values at the beginning and the end of the mass event of interest. dx k( T) f ( x) dt (2) where K(T) is a temperature-dependent reaction rate constant and f(x) is a dependent kinetic model function. There is an Arrhenius type dependency between k (T) and temperature according to Eq. (3) E K( T ) Aexp (3) RT where A is the pre-exponential factor (usually assumed to be independent of temperature), E the apparent activation energy, T the absolute temperature and R is the gas constant. For non-isothermal conditions, when the temperature varies with time with a constant heating dt rate, Eq. (2) is modified as follows: dt dt E Aexp f ( x) (4) dt RT The use of Eq. (4) supposes that a kinetic triplet (E, A, f(x)) describes the time evolution of a physical or chemical change. Upon integration Eq. (4) gives: x T dx A E AE E g( x) exp dt p (5) f ( x) T RT R RT 9 where T is the initial temperature, g(x) the integral form of there action model and p(e/rt) is the temperature integral, which does not have analytical solution. If T is low, it may be reasonably assumed that T, so that the lower limit of the integral on the right-hand side of Eq. (5), T, can be approximated to be zero. The isocnversional integral method suggested independently by Flynn and Wall [17] and Ozawa [18] uses Doyle's approximation [19]. This method is based on the equation: (6) Thus, for x=const., the plot ln β vs (1/T), obtained from thermo grams recorded at several heating rates, should be a straight line whose slope can be used to evaluate the apparent activation energy. In case of BTP for estimation of kinetic assuming the reaction to be first order using Coats- Redfern method [2] has been used. The weight loss or conversion is converted to a normalized form α and is called reaction progress with temperature. For non isothermal TGA the reaction progress is given by m m T (1) ( m m ) Where m T is the sample weight at temperature T, m is the initial weight and m is the final weight of sample. The Arrhenius parameters, for the thermal decomposition of the samples were determined considering [18]. 315

4 TG(%wt) International Journal of Emerging Technology and Advanced Engineering This method uses the integral form of rate law. The rate law of any solid phase reaction can be given as d RT Ae E (2) dt In non-isothermal TGA experiments the heating rate is varied as a function of time d d * dt (3) dt dt dt dx d * dt dt (4) Where is the heating rate given by dt dt E d ( A RT ) e (5) dt is the heating rate. Assuming the reaction to be of first order and integrating and taking logarithm on both sides we get ln(1 ) AR 2RT E ln ln (6) for n T E E RT =1 ln(1 ) AR E ln ln (7) 2RT T E RT E << 1) C/min 4. 7C/min 2. 1 C/min. 15 C/min C/min Temperature ( C) Fig 2 TG Curves 2 A plot of ln ln(1 ) / T Vs 1/T will give the activation energy and frequency factor. IV. RESULTS AND DISCUSSION 4.1 Kinetics based on TGA A three stage decomposition weight loss is observed from Figure 2.In first stage hemicellulose, in second and third stage the degradation of cellulose and lignin may take place respectively [7]. Figure 2 reflects the similar TG curves pattern for all the heating rates, however rates are varying. The degradation occurs at a faster rate in second stage compared to first and third stage as heating rate increases. The weight loss increases in all stages at a faster rate with increase in heating rate. In first stage almost 5-6% of the total weight and in second and third stages 55-6% and 35-4% of the total weight has been decomposed for the all the heating rates. Fig 3 DTG Curves Figure 3 represents DTG curves. Corresponding to the three-stage weight loss on the TG curves, three peaks are observed on the DTG curves. It can be observed that as heating rates increase there is a lateral shift towards higher temperatures of DTG curves and which may be due to the combined effects of the heat transfer at different heating rates and the kinetics of the decomposition resulting in delayed decomposition [8]. Figure 4 and Figure 5 show the values of kinetic constants and there values increase with rise in heating rate may because at high heating the reaction occurs at faster rate due to high temperature and decomposition occurs and so activation energy increases and also increase in molecules collision and so the value of pre-exponent frequency factor increase. The results show that major decomposition occurs in the temperature range of 22 C- 545 C and remaining fraction is ash content. The decomposition may be started with hemi cellouse, cellouse and finally lignin decomposed. In case of all the heating rates the trend is similar. Figure 6 represents the peak value of DTG temperature corresponding to various heating rates. 316

5 Tmax corresponing to DTGmax Activation Energy (kj/mol) lna International Journal of Emerging Technology and Advanced Engineering News Paper 15 1 News paper 2 1st stage 2nd stage 3rd stage 5 1st Stage 2nd Stage 3rd Stage Figure 4 Activation Energy for News paper 36 Figure 5 Frequency Factor at Different Heating Rates News paper Heating Rate ( C/min) Fig. 6 T max Corresponding to DTG max 4.2 Kinetics of Batch Type Pyrolyser Figure 7 show the decomposition of newspaper waste with respect to temperature in three stages I, II and III of decomposition. From Figure 7 it is seen that the decomposition of newspaper waste takes place in three stages: 1.Hemicellulose 2.Cellulose 3.Lignin and printing ink in case of BTP [8]. Figure 8 and Figure 9 indicate the values of kinetic constants in case of BTP at heating rate of 1 C/min. I II III Fig 7 Weight Loss w.r.t.temperature 317

6 Activation Energy (kj/mol) lna International Journal of Emerging Technology and Advanced Engineering The first stage decomposition ends at 15.6 % weight loss and corresponding temperature is C.The second and third stage decomposition terminates after 33.8 % and 68.2 % and corresponding temperatures are C and 6.7 C respectively. Table 4 shows kinetics constants have been obtained for reaction occurred in BTP which indicates that the decomposition occurred in first stage was at slower rate st stage 2nd stage 3rd stage Figure 8 Activation Energy for News paper News Paper 4.3 Comparative Study of TGA and BTP for News Paper Waste as decomposition trend was almost flat while in second and third stages where decomposition occurred at the faster rate. The values of activation energy were justifying decomposition in all three stages. At the same time due to rise in the temperature the value of lna increases due to enchantment in molecular collision News Paper 1st stage 2nd stage 3rd stage Figure 9 Frequency Factor at Different Heating Rates Fig 1 Comparative Decomposition Analysis of TGA and Batch Type Pyrolyser Figure 1 shows comparison of decomposition in case of TGA and BTP in nitrogen atmosphere and at 1 C/min heating rate. The decomposition in case of BTP is not so step as TGA due to thermal resistance of system. The decomposition behavior is same in both TGA and BTP but decomposition curves are not overlapping due to mass transfer resistance according to which in case of BTP as mass of sample is large so thick layers formed in crucible and when heat is penetrated from one layer to the next due gases evolve which resist the heat penetration from one layer to next and due to thermal resistance between two conjugative layers. The size of reactor is large and so some heat loss occurs to the surrounding and so availability of heat for decomposition also decreases in case of BTP at higher temperature than TGA as shown in Figure 1. Figure 11 and Figure 12 include values of kinetic constantans in case of TGA and BTP. Figure 11 and 12 represent that decomposition occurs in three stages in case of BTP and TGA. In case of BTP in first stage the decomposition occurs at a slower rate compare to TGA; while in case of second and third stage of BTP the decomposition rate is lower compare to TGA because of heat and mass transfer resistance. 318

7 Activation Energy (kj/mol lna International Journal of Emerging Technology and Advanced Engineering TGA BTP TGA BTP 1st Stage 2nd Stage 3rd Stage Figure 11 Activation Energy in case of TGA and BTP 1st Stage 2nd Stage 3rd Stage Figure 12 Frequency Factor in case of TGA and BTP V. CHAR CHARACTERSATION The char which remain after the decomposition of newspaper waste at 1 C/min is analyzed with the help of in scanning electron microscope (JEOL 561LV) with Energy Dispersive Spectroscopy (EDS). EDS is an analytical technique which utilizes x-rays that are emitted from the specimen when bombarded by the electron beam to identify the elemental composition of the specimen. Figure 13 Photograph of News paper Char (1 C/min) Figure 14 Elemental Spectrum of News paper Char (1 C/min) Table II Elements in Newspaper Char (1 C/min) Element C O Na Mg Al Si S Ca Fe Total Weight% Table 7 shows the existence of different elements in char of newspaper after TGA at heating rate of 1 C/min which is helpful to select the method for extracting some of the important elements from the char as well as to decide the possible use of char in power plant as a blending mixture. VI. CONCLUSION In case of micro and macro level decomposition of News paper the decomposition occurs in three stages but due to sample size in case of BTP the temperature is higher and so values of activation energy is also high which may also due to heat and mass transfer resistance. 319

8 International Journal of Emerging Technology and Advanced Engineering REFERENCES [1] Report of Kurian Joseph, Perspectives of Solid Waste Management in India, Center for Environmental Studies, Anna University, Chennai 22 [2] Sudhir Kumar, Technology options for municipal solid waste-toenergy project, TERI Information Monitor on Environmental Science, 5(1), 2 [3] Akolkar, A.B. Assessment of the status of municipal solid waste management in metro cities, state capitals, class I cities, and class II towns in India: An insight Volume 29, Issue 2, February( 29), Pages [4] Morcos V.H, Energy recovery from municipal solid waste incineration A review, Heat Recovery Systems and CHP, 9, 1989, [5] Saxena S.C., Jotski C.K., Fluidized-bed incineration of waste materials Progress in Energy and Combustion Science [6] Garcia A.N., Marcilla A., Font R., Thermogravimetric kinetic study of the pyrolysis of municipal solid waste, Thermochimica Acta,254,1995, [7] Chao-Hsiung Wu, Pyrolysis Kinetics of Paper Mixture in Municipal Solid Waste, Journal of Chem.Tech.Biotechnol., Volume 66 (1997), [8] L.Sorum et al, Pyrolysis Characteristics and Kinetics of Municipal Solid Waste Fuel 8 (21) [9] JIN Yu-qi, Study on the comprehensive combustion kinetics of MSW, Journal of Zhejiang University Science 23 [1] Chao- Hasiung Wu, Pyrolysis Product Distribution of Waste Newspaper in MSW, Journal of Analytical and Applied Pyrolysis, Volume 6, March 22, [11] Bhuiyan M.N.A, Murakmai K. and Ota M. 28 on Thermal Stability and Chemical Kinetics of Newspaper Waste by Thermogravimetric and Pyrolysis Analysis Journal of Environment and Engineering 3: [12] P. Grammelis, P. Basinas, A. Malliopoulou, G. Sakellaropoulos, Pyrolysis kinetics and combustion characteristics of waste recovered fuels, Fuel 88 (29) [13] David C., Salvador S., Dirion J.L. and Quintard M., Determination of a reaction scheme for cardboard thermal degradation using thermal gravimetric analysis, J. Anal. Appl. Pyrolysis 67, /323 [14] Kuen-Song Lin, H. Paul Wang, S.-H. Liu, Ni-Bin Chang, Y.-J. Huang, H.C. Wang,Pyrolysis Kinetics of Refuse-Derived Fuel, Fuel processing technology, volume 6,May 1999, [15] Ch. Pasel, W. Wanzl, Experimental Investigation on Reactor Scale-up and Optimization of Product Quality in Pyrolysis of Shreader Waste, Fuel Processing Technology, Volume 8, January 23, [16] Ojolo S. and Bamgboye A. 25 Thermo chemical Conversion of Municipal Solid Waste to Produce Fuel and Reduce Waste Agricultural Engineering International: the CIGR E-Journal 7 [17] J. Flynn, L.A. Wall, quick direct method for the determination of activation energy from thermogravimetric data, Polym. Lett. 4 (1966) [18] T.Ozawa, A new method of analyzing thermogravimetric data, Bull. Chem. Soc. Jpn. 38 (1965) [19] C. Doyle, Kinetic analysis of thermogravimetric data, J. Appl. Polym. Sci. 5 (1961) [2] Yourlmaz S, 26 Investigation of emissions and combustion kinetics of waste wood samples with thermal and spectral methods Post Graduate Dissertation, Middle East Technical University. 32